Photoinduced current transient spectroscopy in high-resistivity bulk materials: Instrumentation and methodology

Abstract

A sensitive photoinduced current transient spectroscopy technique using a computer for data acquisition and processing has been worked out. It enables one to determine separately the signatures and concentrations of deep levels in high-resistivity bulk materials. In a previous paper, possible signal processing has been analyzed from a rather theoretical point of view. In the present report, the instrumentation used as well as the experimental procedure and some practical and complementary aspects will be discussed. For the determination of reliable trap signatures, we have proposed and tested a four-gate data treatment that eliminates, or at least reduces, many of the problems encountered when using the usual double-gate procedure provided some experimental precautions are taken. Yet the double-gate method is useful when one wants to estimate the trap concentrations. A standard experimental procedure is presented that takes into account the temperature dependence of the mobility/free-lifetime product of thermal emitted carriers, and its possible variation during the relaxation of the traps.